A conventional metal plate having a high strength is disclosed in Japanese patent Laid-open publication No. 1 (1989)-172421 published without examination on Dec. 6, 1989. The metal plate has a flat portion, a plurality of first wave portions and a plurality of second wave portions.
The first wave portions extend in a direction parallel with each other. The second wave portions extend parallel to one another in the same direction as the first wave portions. The first wave portions and the second wave portions are disposed alternately.
The first wave portions have a plurality of equally spaced first mound portions projecting from the flat portion in the thickness direction. The first mound portions are surrounded by the flat portion.
The second wave portions have a plurality of equally spaced second mound portions projecting from the flat portion in the same direction as the first mound portions. The second mound portions are surrounded by the flat portion. Thus, the second wave portions have the same shape as the first wave portions, but are shifted in the extending direction by substantially 1/2 of a wave length.
In the above-described metal plate, the first and second mound portions project from the same side of the flat portion in the thickness direction. Although, the metal plate is stronger than a flat metal plate without wave portions, since only the first and second mound portions are formed on the flat portion, the stiffness of the metal plate is higher than the stiffness of a flat metal plate. Hence, deflection of the above metal plate is lower than the deflection of a flat metal plate.
If the metal plate is used for a lift arm of a window regulator connected to a window glass which moves in three dimension, the lift arm may not follow the three dimensional movement of the window glass when the window glass goes up and down due to low deflection of the metal plate. This causes the window glass to operate slower and noisier.
In light of the foregoing, there is a need for a flexible metal plate having a high strength, which addresses at least the foregoing drawback of the related art.